Domain valuation?

[tight fart]

I own ashort . com, an American company, A short inc, have approached me to see if I'd sell, I get a lot of their emails via a catch all address, (they use ashortinc.com and senders miss the inc bit) I think they are a small property management company. Any ideas on how I'd get a sensible valuation?
I do use ashort.com on 2 company vehicles as it's an easy .com to remember.

[tight fart]

Yes, www.ashort.com

[tight fart]

I suggested an offer of around $5k, not heard from them again.